A vehicle body is manufactured by at least welding a floor, side panels and a roof to one another. Recently, the vehicle body is automatically assembled using jigs and robots (see, e.g., patent literature 1 below).
The vehicle body disclosed in patent literature 1 is comprised of a floor, side panels, and a roof. Using setting jigs, the side panels are forcefully pressed against the floor to maintain a regular interval between the side panels. The roof is placed onto the side panels with the regular interval therebetween being maintained, and the floor, the side panels, and the roof are welded by welding robots.
Although the foregoing conventional assembling method is widely put in practical use, the method leaves room for improvements. Using the setting jigs to forcefully press the side panels against the floor to maintain the regular interval between the side panels is usually done. Under this condition, the welding is conducted. However, upon removal of the setting jig after the welding, the floor is released from the compressive deformed position. This results in vehicle bodies increasing their width dimension, including vehicles increasing their width dimensions within the tolerance. The degree of change in with dimension is different from vehicle body to vehicle body, which constitutes a factor for variation in width dimension among the vehicle bodies. Further, as for the welding with the compressive force applied to the floor, a stress remains upon elimination of the compressive force. This remaining stress becomes a factor for occurrence of distortion. There is a demand for an assembling technique which eliminates the factor for variation in dimension among the vehicle bodies and prevents or reduces the occurrence of distortion.
As disclosed in patent literature 1, furthermore, the setting jig carries the welding robot thereon, and thus is complicated and large-sized. Although a space for installation of the jig is defined on a lateral side of the vehicle body, such a space is limited and thus the setting jig needs to be simplified for installation in the limited space.
As disclosed in patent literature 1, furthermore, the roof hanging on a retainer attached to a travelling frame is conveyed to a predetermined location. The travelling frame is a steel grid-shaped frame having the overall length larger than that of the roof, and thus is heavy and large-sized. The welding robot is carried adjacent to this travelling frame. For this reason, the assembling station is large-sized and heavy. While there is a demand for reduction in size and weight of the assembling station, the reduction in size and weight of the travelling frame associated with the roof is required.